1. Technical Field
The present invention generally relates to a communication module for a vehicle data communication system. More particularly, the present invention is directed to an I/O module which is disposed between a primary vehicle controller and a communication network, such as an SAE J1850 serial communication data bus or other suitable communication network, for alleviating the I/O processing burden of the primary vehicle controller.
2. Discussion
Automotive vehicles are commonly equipped with multiple-access serial data communications networks to enable data transfer between various electronic components within the vehicle. The Society of Automotive Engineers (SAE) has established the J1850 class data communications network which has become widely accepted throughout the automotive industry. The J1850 protocol is a set of technical requirements and parameters which specify the use of symbols for communicating serial data over a one or two-wire communications bus.
The J1850 protocol is based on a medium-speed (Class B) serial multiplex communication protocol specifically intended for use in automotive vehicles. Serial multiplex communication (MUX) is a method of reducing wiring requirements while increasing the amount and type of data which may be shared between various electronic components connected to the communication network. This technique is achieved by connecting each component, or node, to a serial bus, consisting of either a single wire or a twisted pair of wires. Each node collects whatever data is useful to itself or other nodes (i.e. wheel speed, engine rpm, oil pressure, etc.), and then transmits this data onto the J1850 bus, where any other node which needs this data can receive it. This data sharing technique reduces wiring and eliminates the need for redundant sensing systems.
In one exemplary implementation, two or more microprocessor based controllers are positioned throughout the vehicle and communicate with each other along the J1850 data bus. Each controller will periodically transmit information in the form of message data organized into a single message frame. This transmission can take place after the controller determines that the data bus is free. Once this message frame is transmitted onto the J1850 bus, this information is available to either a specific node, such as another controller, or all of the nodes on the data bus depending on the type of messaging scheme implemented.
An additional feature of the J1850 protocol allows one or more of the nodes to respond to the original data message within the same message frame (i.e. within a short period of time after receiving the original message, but before another node begins transmitting a new message frame). Within the J1850 protocol, this is referred to as an xe2x80x9cin-frame responsexe2x80x9d (IFR). Accordingly, the J1850 protocol design provides a single wire network through which information can be exchanged between various controllers connected to the data bus. For example, the engine controller and the transmission controller may exchange information via the J1850 data bus concerning real-time operating or performance conditions of their associated systems. However, monitoring the data bus places an additional burden on the controller,
Therefore, it is desirable to provide a communication module for improving the performance of the primary controller in a vehicle data communication system by reducing the processing burden placed on the controller for transmitting and processing non-critical data messages. It is further desirable to provide a communication module that can be pre-programmed with an initial set of communication tasks, and sequence through the set of tasks for minimizing interaction between the primary controller and the communication module.
The present invention is directed to a messaging system for a vehicle. The messaging system includes a primary controller for transmitting and receiving information. The primary controller generates an array of data messages. A communication module is connected to the primary controller for receiving and storing the array of data messages in a memory. The communication module includes a sequencing controller for sequencing through the memory and selecting individual data messages from the array of data messages. A data bus is connected to the communication module and provides a communication link between at least one additional vehicle node connected to the data bus.